MOFs and surface modification synergistically modulated cellulose membranes for enhanced water permeability and efficient tellurium separation in wastewater

Abstract

With the widespread use of tellurium-containing products such as cadmium telluride solar cells in daily life, tellurium-containing wastewater inevitably enters the environmental water system. Removal of the ionic contaminant tellurite is essential in wastewater reclamation due to its potential threat to human health and difficulty of elimination. Herein, a rational design of separation membranes with synergistic physical and chemical effects to enhance separation efficiency with almost complete compensation for the loss of water flux was proposed. Membranes for tellurium separation with high efficiency and enhanced water flux were prepared by surface modification on the MOF-based support layer forming a dense separation layer (TSNTCM). The membrane separation efficiency was enhanced by the introduction of NH2-MIL-125 in the support layer, while the water flux was improved by its nano water channels. The abundant hydroxyl and anionic groups in the structure of the polymer monomer sodium lignosulfonate not only endowed the separation layer with chemical interaction (hydroxyl substitution), but also made the membrane surface highly negatively charged and improved the physical interaction. TSNTCM showed excellent tellurium separation efficiency (>95%) over a wide concentration range and achieved the highest rejection (99.16%) at pH = 6. Besides, the rejection of tellurium by TSNTCM was above 90% in the presence of common coexisting ions, but decreased in the presence of selenite, which may be due to the similar structure and properties of selenite and tellurite. Moreover, TSNTCM demonstrated satisfactory reusability and anti-fouling properties. Overall, MOFs and surface modification enhanced the comprehensive performance of TSNTCM, providing great potential for its application in wastewater reclamation.